A sensory neurone carries an electrical impulse from a sound receptor in the cochlea to the central nervous system. Electrode P is placed on its axon close to the cell body. Electrode Q is placed on the same axon close to the terminal branches, which form synapses with neurones in the central nervous system.
Which statement correctly describes the expected recordings and what happens at these synapses?
Q records the impulse before P; neurotransmitter is released into the synaptic gap
P records the impulse before Q; neurotransmitter is released into the synaptic gap
P records the impulse before Q; receptor molecules are released into the synaptic gap
Q records the impulse before P; the electrical impulse crosses the synaptic gap directly
111 exam-style questions on Edexcel GCSE Biology 2.3 The nervous system and brain, covering 2.3.1 Structures and functions of the brain, 2.3.2 Imaging brain function with scanning, 2.3.3 Limitations in treating nervous system damage, 2.3.4 Neurones and impulse transmission, and 2.3.5 Structure and function of a reflex arc. Each one has a worked solution and a mark scheme showing where the marks go.